Currently in the fastener industry, the most common type of fastener head styles are the “Flanged hex head” and the “Hex head.” Referring to FIGS. 1(a) and 1(b), the “flanged hex head” and the “hex head are generally represented by the numerals 100a and 100b, respectively. These head styles both utilize a hex shaped head 102 for application of driving torque. The flanged hex head utilizes an integrated flange 104 at the base of the hex shaped head 102 to enhance application and distribution of the clamp-load of the fastener 100 caused by the engagement of the threads 106 with the internal threads of the work piece (not shown).
With common hex heads, only a very small portion of each facet of the hex may be utilized for torque application. This is due to the fact that the tool utilized to drive the hex head is also hex-shaped (some are twelve-sided or other variations). Because the tool's internal hex may be slightly larger dimensionally than the hex of the fastener (in order to slip over it freely), during initial driving the tool rotates slightly before it contacts the fastener hex (see FIGS. 2(a) and 2(b)).
When such contact is made, there may only initially be a “point” contact 208 between the corners 210 of the fastener hex 102 and the internal facet of the tool, viewed down the axis of the fastener as shown in FIG. 2. As torque application continues, local deformation of the fastener's hex corners 210 may result in this contact expanding to be more of a rectangular contact point between the internal facet of the tool and the deformed facet 314 of the fastener hex 102 shown in FIG. 3. A rectangular area 312 of the facet 316 varies in size and shape depending on fastener metallurgical properties, the amount of taper in the fastener 100, and the initial gap between the tool 220 and the facets 316 of the hex head 102. The area of this contact may be no more than ten percent of the surface area of each facet 316, and it may not extend beyond approximately ten percent from any corner of the hex head 102 (where facets 316 join together).
Similar contacts may be made during loosening of the fastener 100, e.g., rotational direction opposite tightening direction, except that this contact may occur on an area 314 of the opposite end of each hex facet 312. Therefore, the contact area 314 for loosening of the fastener 100 may be the mirror image of the tightening area 312, but is located at the opposite end of each facet 316 adjacent to each corner (where the facets 316 intersect). During installation and removal, the tool 220 may not contact the centers of the facets 316, and the area around the centers. Therefore, most of the surface areas of the hex head facets 316 may never be utilized and may not be necessary for either tightening or loosening the fastener 100.
The purpose of the application of torque to a hex-shaped fastener head is to revolve the fastener 100 axially, thus causing the thread helixes of the mating parts to engage. Ultimately, the loading thusly applied is transmitted through the fastener 100 to its bearing surface, creating a spring-load in the fastened joint. Since only a small portion, e.g., facet portions 312 and 314 of the fastener hex head 102, are required, present technology fastener hex heads 102 contain much more material than required for this purpose, with that material located in places that are hardly ideal. For example, in many fastener usages, the fastener 100 is presented to its mating internally threaded part (not shown) by holding it in the fingers of one hand. Usually, this is accomplished by gripping it between the tips of the thumb, forefinger, and middle finger. The surfaces of a hex are not ideally suited for this purpose.
Further, the shape of the fastener head may be important to the ease with which the head is handled by an operator. Referring now to FIG. 4, depicted is a schematic plan diagram of a hex head fastener being grasped by representations of fingers of a hand. The hex head 402 may be grasped (e.g., gripped) by the thumb 404, forefinger 406, and middle finger 408 of one hand (not shown). During the gripping of any small object with the fingers 404, 406 and 408, the surfaces of the fingers 404, 406 and 408 presented to the hex head 402 are essentially convex curved surfaces of variable size. These surfaces are normally presented to grip the hex head 402 in a manner such that they are essentially equally distributed about the hex head 402 at approximately 120 degrees apart. As the hex head 402 is grasped, the convex curved surfaces of the fingers 404, 406 and 408 may deform to match the contour of the surfaces being grasped so that it may be relatively more “finger friendly.”
These problems, among others, result in fasteners which are heavier, more costly than necessary, and ill-suited for both hand and tool assembly. While some other prior technologies have addressed the phenomena of inefficient load application by creating special tools and driving surfaces, and other technologies have addressed material reduction by hollowing out the center of the hex head 102 through various means, while still other technologies have created three-cornered heads with special driving tools, none of these technologies have addressed the hex head 102 as a whole, considering the real current shape of the hex-head production part, as well as its interaction with tools in the industry. Current technology hex heads contain much more material than may be required for its intended purpose, and with material located in places that are hardly ideal for handling, and cost and weight reduction.